This scientifically valid advice comes from the staff at Cook's Illustrated, who note that "garlic is one product where a strong fragrance is a sign of questionable quality rather than potency. "
Because this recommendation is so logically counterintuitive, try reasoning out the rationale for it before peeking at the explanation below the fold (and at the link).
Garlic releases its aroma when cells have been damaged, so a clove in the store that smells "garlicky" has probably been traumatized in transport. The staff at Cook's Illustrated confirmed this by whacking heads of garlic with a rolling pin (lightly, without producing visible damage). After a few days the injured (and fragrant) garlic heads were "soft and beginning to rot in multiple places," while control (nonaromatic) garlic heads were firm.